Compact reciprocating piston machine

ABSTRACT

Reciprocating piston machine in which a yoke member reciprocates within a piston in a direction normal to the direction of piston movement. Roller bearings are provided between the yoke member and piston, and means is provided for preloading the bearings and adjusting the position of the piston. A reversible sealing ring utilizes the pressure differential across the piston to enhance the seal in one direction, and each end of a double-ended piston can be operated in either a vacuum or a pressure mode.

United States Patent [191 Hartley 1 COMPACT RECIPROCATING PISTON MACHINE [76] Inventor: Ezra Dale Hartley, 2700 Jalmia Dr.,

Los Angeles, Calif. 90046 [22] Filed: June 7, 1972 [21] Appl. No.: 260,480

[52] US. Cl. 417/535 [51] Int. Cl. F04b 25/00 [58] Field of Search 74/50; 92/ 182, 241; I 417/534 [56] References Cited UNITED STATES PATENTS 734,595 7/1903 Olin 74/50 997,480 7/1911 Twombly 74/50 1,190,949 7/1916 Phillippe 74/50 1,749,212 3/1930 Elliott 92/74 2,295,160 9/1942 Christenson 92/241 2,366,237 l/l945 Clausen 74/50 2,562,639 7/1951 Platner 92/74 2,613,651 10/1952 Herreschoff 92/74 2,637,606 5/1953 Pielop, .Ir 92/241 2,686,402 8/1954 Samuel 92/182 [4s] Sept. l0, 1974 2,727,471 12/1955 Martin 92/182 3,744,936 7/1973 Sadler 417/536 FOREIGN PATENTS OR APPLICATIONS 654,331 12/1962 Canada 417/534 588,341 5/1947 Great Britain 417/534 496,190 10/1950 Belgium 92/182 Primary Examiner-William L. Freeh Attorney, Agent,- or Firm-Flehr, l-lohbach, Test, Albritton & Herbert 8 Claims, 7 Drawing Figures COMPACT RECIPROCATING PISTON MACHINE BACKGROUND OF THE INVENTION This invention pertains generally to reciprocating piston machines and more particularly to a compact machine without connecting rods.

Reciprocating piston machines, whether operated as pumps or engines, commonly have connecting rods and wrist pins for transferring the power between the pistons and a crankshaft. Heretofore, in order to reduce size, there have been some attempts to construct a re ciprocating piston machine with a slider mechanism, such as a Scotch yoke, instead of connecting rods and wrist pins. In mechanisms of this type, an eccentric drive shaft or output shaft rotates in a slider or yoke member which is slidably mounted in a piston assembly for reciprocating movement in a direction normal to the direction of piston movement. Slider mechanisms heretofore provided have been subject to certain disadvantages such as high frictional losses and limited load capacity. In addition, the prior slider mechanisms have required a finite amount of clearance to prevent lock up of the mechanism, and this clearance has resulted in undesirable backlash.

SUMMARY AND OBJECTS OF THE INVENTION In the compact machine of the present invention, bearings are provided between the yoke member and piston, and all loads are supported on rolling surfaces. Means is provided for preloading the bearings to eliminate backlash and align them in such manner that the load is distributed evenly among them. The position of the piston assembly can be adjusted at the time the bearings are preloaded, and head clearance can be equalized between both ends of a double-acting piston. Bumpers limit the travel of the bearings and make proper positioning of them an automatic procedure. A reversible sealing ring carried by the piston utilizes the pressure difference across the piston to provide a more efficient seal in one direction, and this permits either end of a double-ended piston to function equally well in a pressure or vacuum environment.

It is in general an object of the present invention to provide a new and improved compact reciprocating piston machine.

Another object of the invention is to provide a machine of the above character in which all loads are supported on rolling surfaces and frictional losses are minimized.

Another object of the invention is to provide a machine of the above character which includes means for preloading the rolling elements and adjusting the position of a piston in its cylinder.

Another object of the invention is to provide a machine of the above character which includes a reversible seal ring which is aided by pressure differences across the piston.

Additional objects and features of the invention will be apparent from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view, partially sectioned, of one embodiment of a double-acting pump incorporating the present invention.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view taken along line 33 of FIG. 1, with the drive shaft rotated in a clockwise direction.

FIG. 4 is an exploded isometric view of a portion of the piston and yoke assembly of the machine shown in FIG. 1.

FIG. 5 is an enlarged cross-sectional view of the reversible sealing ring of the machine shown in FIG. 1.

FIG. 6 is an enlarged cross-sectional view of an alternative embodiment of a reversible sealing ring for use in the machine of FIG. 1.

FIG. 7 is an exploded isometric view of one embodiment of a pump having a pair of double-acting pistons incorporating the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pump illustrated in FIGS. 1-4 includes a housing 11 in which a longitudinally extending bore 12 is provided. Cylindrical sleeves 13 are mounted in counterbores 12a at each end of bore 12. The ends of the bore are closed by means of head assemblies 14 comprising valve plates 16 and covers 17. The covers are secured to housing 11 by means of screws 18, and the valve plates are clamped between sleeves l3 and the covers. O-rings 19 provide seals between the valve plates, covers and housing.

A longitudinally movable piston assembly 21 is disposed within housing 11 and cooperates with sleeves 13 to form chambers of variable volume 22 at the ends of bore 12. The piston assembly includes a body or skirt member 23 and a pair of head members 24 which are attached to body member 23 by means of screws 26. A pair of sealing rings 28, 29 are provided at each end of the piston assembly. The rings 28 are conventional annular rings fabricated of a resilient rigid material, and they are mounted in annular grooves 31 in piston body 23. Rings 29 are made of a resilient material such as Teflon, they are generally U-shaped in cross section and they are mounted in annular grooves 32 formed in the sides of piston head members 24. Rings 28 and 29 provide slidable seal between the piston assembly and the inner walls 13a of sleeves 13. As is discussed more fully hereinafter, rings 29 are reversible in their grooves, and they can be oriented according to the type of pumping action desired at each end of the piston assembly.

Piston body member 23 is formed to include an aperture 34 in which a yoke member 36 is mounted. The yoke member has a cylindrical bore 37 through which a drive shaft 38 extends. Shaft 38 is mounted in ball bearing assemblies 39 carried by housing .11 and is thereby adapted for rotation about an axis 41 extending normally of the direction of piston movement. Shaft 38 includes an enlarged cylindrical portion 38a eccentric to axis 41. This portion of the shaft is rotatably mounted in bore 37 of the yoke member by means of a roller bearing assembly 42.

Generally planar roller bearing assemblies 44 provide rolling movement of yoke member 36 in piston aperture 34. Each of these bearing assemblies includes a plurality of rollers or needle bearings 46 and a cage 47. Rollers 46 engage generally planar bearing surfaces 48 which are provided on yoke member 36. Bumpers 49 are provided at the ends of bearing surfaces 48, and

they limit the travel of the bearing assemblies 44. These bumpers are preferably spaced apart by a distance slightly greater than the sum of the length of cage 47 and one-half of the eccentricity of drive shaft 38. Rollers 46 also engage race members 51 which are carried by the piston assembly. Each of these race members includes an inwardly facing surface 52 and an outwardly extending threaded stem 53.

Means is provided for preloading bearing assemblies 44 and adjusting the position of yoke member 36 in piston aperture 34. This means includes adjusting nuts 56 having internal threads 57 which engage threaded stems 53 of race members 51. The adjusting nuts are seated in sockets 58 formed in head members 24 of the piston assembly. Slots 59 are provided in the adjusting nuts, and access to these slots is provided by means of openings 61 in the piston head members. O-rings 62 provide seals between the adjusting nuts and head members.

Inlet ports 63 and discharge ports 64 are provided in covers 17, and check valve assemblies 66 and 67 control communication between these ports and chambers 22.

Each inlet valve assembly 66 includes a generally planar valve member 68 movable between open and closed positions and a recessed seat 69 formed in the inner wall of valve plate 16. An O-ring 71 provides a seal between valve member 68 and seat 69 when the valve member is in its closed position. A compression spring 72, constrained between the outer wall of valve plate 16 and a keeper 73 attached to valve member 68 by a screw 74, urged the valve member toward its closed position. A plurality of flow passageways 76 in the valve plate provide communication between port 63 and chamber 22 when valve assembly 66 is opened.

Each discharge valve assembly 67 includes a conically tapered poppet member 77 and a matching seat 78 formed in valve plate 16. A compression spring 79, constrained between poppet member 77 and a retainer 81, urges the poppet member into its closed position. Flow passageways 82 formed in retainer 81 provide communication between discharge port 64 and chamber 22 when valve assembly 67 is opened.

It should be noted that when the inlet and discharge valve assemblies at one end of the piston are closed, the valve plate and valve members present a substantially flat surface. There are no voids or dead spaces, and a high volumetric efficiency or compression ratio are possible.

As indicated previously, seal rings 29 are generally U-shaped in cross section. Referring now to FIG. 5, it can be seen that each of these seal rings includes a pair of spaced apart annular lip portions 29a which engage the inner wall of cylindrical sleeve 13 and bottom wall 32a of groove 32. A resilient member 84 is provided within seal ring 29. This member has a generally U- shaped cross section, and it urges the lip portions of the seal ring against the walls of the sleeve and groove. The open end of the seal ring is oriented toward the high pressure end of the piston, and the pressure differential across the piston serves to further urge the lip portions of the ring into sealing engagement with the walls of the sleeve and groove. With seal rings 29 oriented as shown in FIG. 1, the right end of the pump is particularly adapted for vacuum service, and the left end is particularly adapted for pressure service. As indicated previously, the rings can be reversed in their grooves to reverse the modes of operation for which the ends of the pump are best suited.

FIG. 6 illustrates a seal ring 86 which is generally similar to the ring shown in FIG. 5. Ring 86 is generally U- shaped, and it has a pair of spaced apart annular lip portions 86a which engage the walls of sleeve 13 and groove 32. The lip portions of this ring have inclined ridges which further enhance the effectiveness of the seal in one direction. A resilient member 87 disposed within seal ring 86 urges the annular lip portions against the walls of the sleeve and groove. This seal ring is also reversible within the groove, and the open portion of the ring is generally oriented toward the high pressure end of the piston.

Operation and use of the pump shown in FIGS. 1-4 can be described briefly. When drive shaft 38 is rotated, piston assembly 21 moves longitudinally, alternately enlarging and decreasing the volumes of chambers 22, and yoke member 36 moves back and forth in piston aperture 34. As chambers 22 are enlarged and decreased, inlet and outlet valve assemblies 66 and 67 open and close, and air or another fluid can be pumped from inlet ports 63 to discharge ports 64. Connections can be made to the inlet and discharge ports as desired, and depending upon the manner in which the connections are made, the pump may be operated as either a single two-stage pump or as two single-stage pumps for either pressure or vacuum service. It can also be operated as a vacuum pump at one end and a pressure pump at the other.

The bearings can be preloaded and the longitudinal portion of the piston assembly can be adjusted by turning adjusting nuts 56 on the threaded stems of race members 51. Before these adjustments are made, however, drive shaft 38 should be rotated at least one full revolution to assure that bearing assemblies 44 are positioned correctly. If they are not positioned correctly, they will strike bumpers 49 and skid until they are in the correct position whereupon they will roll back and forth between the bumpers without striking them. Once the bearing assemblies are positioned properly, adjusting nuts 56 are adjusted to eliminate backlash and provide the desired preloading. By turning both of the adjusting nuts equally in the same direction, the position of the piston assembly can be adjusted without affecting the preloading of the bearings.

The pump illustrated in FIG.- 7 is generally similar to the pump described above, but it has two double-acting piston assemblies. This pump includes a block 101 in which a pair of longitudinally extending bores 102 are formed. Piston assemblies 21 are slidably mounted in the bores,'and these piston assemblies are driven in the manner described above. The ends of the bores are closed by means of head assemblies 104 which carry inlet and discharge valve assemblies similar to valve assemblies 66 and 67. Drive gears 106 are affixed to drive shafts 38 and mounted in a recessed area 107 in one side of block 101. A cover plate 108 is mounted on this side of the block and encloses the recessed area. A drive motor 111 is mounted on the side plate, and a pinion gear 112 is affixed to the motor shaft and engages drive gears 106. The operation and use of this pump are generally similar to the operation and use of the pump described above.

The invention has several important advantages. All loads are supported on rolling surfaces, rather than sliding elements. This permits a greater load capacity than was possible with slider mechanisms of the prior art, and it greatly reduces frictional losses inherent in the prior art. The bearings can be preloaded to eliminate backlash and to distribute loads evenly among them. The bearings are maintained in the proper position by the bumpers on the yoke member, and the position of the piston assembly can be adjusted to provide proper head clearance at both ends of the piston. The piston is sealed by a ring which utilizes the pressure dif' ference across the piston to form a more efficient seal in one direction. This ring is reversible, permitting each end of the double-acting piston to function equally well in a pressure or vacuum mode. When closed, the valves present a substantially flat surface, free of voids or dead spaces, thereby assuring a high compression ratio or volumetric efficiency. While the invention has been described with specific reference to pumps, it is equally applicable to machines operated as engines.

It is apparent from the foregoing that a new and improved compact reciprocating piston machine has been provided. While only the presently preferred embodi ments have been described, as will be apparent to those familiar with the art, certain changes and modifications can be made without departing from the scope of the invention as defined by the following claims.

I claim:

1. In a reciprocating poston machine, means defining a longitudinally extending cylinder having a side wall and at least one closed end, a longitudinally movable piston disposed in the cylinder and cooperating with the means defining the cylinder to form a chamber of variable volume at the closed end of said cylinder, inlet and discharge valve means providing communication with said chamber, means forming a slidable seal between the piston and the side wall of the cylinder, said piston being formed to include a transversely extending aperture, a yoke member disposed in the aperture and movable transversely of the piston, said yoke member being formed to include a cylindrical bore extending normally of both the direction of movement of the piston and the direction of movement of the yoke member within the piston, a shaft mounted for rotation about a fixed axis parallel to the axis of the yoke bore, said shaft having a cylindrical portion eccentric to the shaft axis and rotatably disposed in said bore, bearing means ex tending transversely between the yoke member and piston to provide rolling movement of the yoke member in the aperture, said bearing means including a pair of generally planar roller bearing assemblies each comprising a plurality of rollers engaging longitudinally spaced-apart bearing surfaces formed on said yoke member and generally planar bearing race members carried by the piston and engaging the rollers opposite the bearing surface of the yoke member, and means for exerting a longitudinal force on the bearing means and positioning the yoke member longitudinally in the aperture.

2. A machine as in claim 1 wherein the means forming the slidable seal includes a ring of resilient material disposed in an annular groove in the side of the piston, said ring having a generally U-shaped cross section defined in part by a pair of spaced apart annular lip portions engaging respectively the side wall of the cylinder and the bottom wall of the groove, the open portion of said seal ring facing toward the high pressure end of the piston.

3. A machine as in claim 1 together with roller bearing means between the yoke member and the cylindrical portion of the shaft.

4. A machine as in claim 1 together with means carried by the yoke member for limiting movement of the rollers transversely of said member.

5. A machine as in claim 1 wherein the cylinder is closed at both ends to form two chambers of variable volume, separate inlet and discharge valve means being provided for each of said chambers.

6. In a reciprocating piston machine, a block having a pair of longitudinally extending bores disposed sideby-side, head assemblies closing the ends of said bores, longitudinally movable pistons disposed in said bores to provide chambers of variable volume at the ends of said bores, inlet and discharge valve means carried by the head assemblies to provide communication with the chambers, said pistons being formed to include transversely extending apertures, yoke: members disposed in the apertures and movable transversely of the pistons, bearing means between the yoke member and the bodies of the pistons, bearing means between the yoke members and the bodies of the pistons to provide a rolling movement of the yoke members in the apertures, the bearing means for each piston including a pair of generally planar roller bearing assemblies each comprising a plurality of rollers engaging longitudinally spaced-apart bearing surfaces formed on the yoke member disposed in the piston aperture and generally planar bearing race members carried by the piston and engaging the rollers opposite the bearing surface of the yoke member, means carried by the pistons for preloading the bearing means and positioning the yoke members longitudinally in the apertures, said yoke members being formed to include cylindrical bores extending normally of both the direction of piston movement and the direction of yoke movement within the pistons, shafts mounted for rotation about fixed axes parallel to the axis of the yoke bores, said shafts having cylindrical portions eccentric to the shaft axis and rotatably disposed to the yoke bores, and drive means engaging the shafts for rotating the same.

7. In a reciprocating piston machine, means defining a longitudinally extending cylinder, a piston disposed in the cylinder, said piston having a pair of longitudinally spaced end walls and an aperture: intermediate the end walls, a yoke member having a transversely extending bore and a pair of longitudinally spaced bearing surfaces disposed in the aperture, an eccentric member rotatively mounted in the bore in the yoke member, a pair of bearing pads disposed in the aperture between the bearing surfaces of the yoke member and the end walls of the piston, said bearing; pads having bearing surfaces facing the bearing surfaces of the yoke member and longitudinally extending threaded portions facing toward the ends of the piston, a plurality of rollers disposed between the bearing surfaces of the yoke member and bearing pads, and threaded members engaging the threaded portions of the bearing pads, said threaded members having semispherical heads received in semispherical sockets formed in the end walls of the piston.

8. A machine as in claim 7 further including roller bearing means mounting the eccentric member in the bore in the yoke member. 

1. In a reciprocating poston machine, means defining a longitudinally extending cylinder having a side wall and at least one closed end, a longitudinally movable piston disposed in the cylinder and cooperating with the means defining the cylinder to form a chamber of variable volume at the closed end of said cylinder, inlet and discharge valve means providing communication with said chamber, means forming a slidable seal between the piston and the side wall of the cylinder, said piston being formed to include a transversely extending aperture, a yoke member disposed in the aperture and movable transversely of the piston, said yoke member being formed to include a cylindrical bore extending normally of both the direction of movement of the piston and the direction of movement of the yoke member within the piston, a shaft mounted for rotation about a fixed axis parallel to the axis of the yoke bore, said shaft having a cylindrical portion eccentric to the shaft axis and rotatably disposed in said bore, bearing means extending transversely between the yoke member and piston to provide rolling movement of the yoke member in the aperture, said bearing means including a pair of generally planar roller bearing assemblies each comprising a plurality of rollers engaging longitudinally spacedapart bearing surfaces formed on said yoke member and generally planar bearing race members carried by the piston and engaging the rollers opposite the bearing surface of the yoke member, and means for exerting a longitudinal force on the bearing means and positioning the yoke member longitudinally in the aperture.
 2. A machine as in claim 1 wherein the means forming the slidable seal includes a ring of resilient material disposed in an annular groove in the side of the piston, said ring having a generally U-shaped cross section defined in part by a pair of spaced apart annular lip portions engaging respectively the side wall of the cylinder and the bottom wall of the groove, the open portion of said seal ring facing toward the high pressure end of the piston.
 3. A machine as in claim 1 together with roller bearing means between the yoke member and the cylindrical portion of the shaft.
 4. A machine as in claim 1 together with means carried by the yoke member for limiting movement of the rollers transversely of said member.
 5. A machine as in claim 1 wherein the cylinder is closed at both ends to form two chambers of variable volume, separate inlet and discharge valve means being provided for each of said chambers.
 6. In a reciprocating piston machine, a block having a pair of longitudinally extending bores disposed side-by-side, head assemblies closing the ends of said bores, longitudinally movable pistons disposed in said bores to provide chambers of variable volume at the ends of said bores, inlet and discharge valve means carried by the head assemblies to provide communication with the chambers, said pistons being formed to include transversely extending apertures, yoke members disposed in the apertures and movable transversely of the pistons, bearing means between the yoke member and the bodies of the pistons, bearing means between the yoke members and the bodies of the pistons to provide a rolling movement of the yoke members in the apertures, the bearing means for each piston including a pair of generally planar roller bearing assemblies each comprising a plurality of rollers engaging longitudinally spaced-apart bearing surfaces formed on the yoke member disposed in the piston aperture and generally planar bearing race members carried by the piston and engaging the rollers opposite the bearing surface of the yoke member, means carried by the pistons for preloading the bearing means and positioning the yoke members longitudinally in the apertures, said yoke members being formed to include cylindrical bores extending normally of both the direction of piston movement and the direction of yoke movement within the pistons, shafts mounted for rotation about fiXed axes parallel to the axis of the yoke bores, said shafts having cylindrical portions eccentric to the shaft axis and rotatably disposed to the yoke bores, and drive means engaging the shafts for rotating the same.
 7. In a reciprocating piston machine, means defining a longitudinally extending cylinder, a piston disposed in the cylinder, said piston having a pair of longitudinally spaced end walls and an aperture intermediate the end walls, a yoke member having a transversely extending bore and a pair of longitudinally spaced bearing surfaces disposed in the aperture, an eccentric member rotatively mounted in the bore in the yoke member, a pair of bearing pads disposed in the aperture between the bearing surfaces of the yoke member and the end walls of the piston, said bearing pads having bearing surfaces facing the bearing surfaces of the yoke member and longitudinally extending threaded portions facing toward the ends of the piston, a plurality of rollers disposed between the bearing surfaces of the yoke member and bearing pads, and threaded members engaging the threaded portions of the bearing pads, said threaded members having semispherical heads received in semispherical sockets formed in the end walls of the piston.
 8. A machine as in claim 7 further including roller bearing means mounting the eccentric member in the bore in the yoke member. 